Thank you for visiting nature.com. You are using a browser version with
limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off
compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site
without styles and JavaScript.

Abstract

Single crystals are typically brittle, inelastic materials. Such mechanical responses limit their use in practical applications, particularly in flexible electronics and optical devices. Here we describe single crystals of a well-known coordination compound—copper(II) acetylacetonate—that are flexible enough to be reversibly tied into a knot. Mechanical measurements indicate that the crystals exhibit an elasticity similar to that of soft materials such as nylon, and thus display properties normally associated with both hard and soft matter. Using microfocused synchrotron radiation, we mapped the changes in crystal structure that occur on bending, and determined the mechanism that allows this flexibility with atomic precision. We show that, under strain, the molecules in the crystal reversibly rotate, and thus reorganize to allow the mechanical compression and expansion required for elasticity and still maintain the integrity of the crystal structure.

Acknowledgements

We thank the Australian Research Council for support. Part of this research was undertaken on the MX1 and MX2 beamlines of the Australian Synchrotron, Clayton, Victoria, Australia. We thank Australian Synchrotron for travel support and their staff for assistance. We thank the University of Queensland, Queensland University of Technology and the Central Analytical Research Facility (CARF, QUT) for support.

Author information

Author notes

Anna Worthy

& Arnaud Grosjean

These authors contributed equally to this work.

Affiliations

School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia

Anna Worthy

, Yanan Xu

, Cheng Yan

& John C. McMurtrie

School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland 4072, Australia

Arnaud Grosjean

, Michael C. Pfrunder

& Jack K. Clegg

Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland 4072, Australia